Physicochemical analysis of water indicated that water temperature (15.9-31.5°C) and pH (6.97-7.6) were suitable for phytoplankton growth. The nutrients concentration of water at study area decreased gradually from hyper-eutrophic at River Nile (site I) to eutrophic at out flow (site VI). The annual mean of phytoplankton species number was 90.1 and 87, which mainly belong to Bacillariophyta (36, 35 species), Chlorophyta (40.6, 39 species), Cyanophyta (12, 11 species) and Dinophyta (1.5, 1.5 species) at drinking water treatment plant intake of El-Bostan (site IB) and Faraskour (site IF) with significant increase during summer months. The annual mean of phytoplankton standing crop was 9435.2 x103 cell/L and 7613.2 x103 cell/L at site IB and IF respectively. These due to high diatom growth (84.7%) followed by Chlorophyta (11.7%) then Cyanophyta (3.6%) and Dinophyta (0.001%). This annual mean of total phytoplankton standing crop was decreased at coagulation-flocculation basin at El-Bostan plant (site IIB) (41.2%), where Bacillariophyta represent 33.2%, Chlorophyta represent 5% and Cyanophyta represent 3%. In addition, at sedimentation basin at El-Bostan plant (site IIIB), it decreased by 42.5%, where Bacillariophyta represent 38.5%, Chlorophyta represent 3.6% and Cyanophyta represent 0.5%. It also decreased at coagulation, flocculation and sedimentation basin at Faraskour plant (site IIIF) (62.7%), in which Bacillariophyta represent 54.8%, Chlorophyta represent 5.3% and Cyanophyta represent 2.6%. Furthermore, it has a considerable decrease at filtration basin at El-Bostan plant (site IVB) (14.9%) and filtration basin at Faraskour plant site IVF (27%) which belong to Bacillariophyta (11.9, 22.3%), Chlorophyta (2.8, 4.4%) and Cyanophyta (0.1, 0.3%) at sites IVB and IVF respectively. While it has a very low decrease at disinfection basin at El-Bostan plant (site VB) (1.4%) and disinfection basin at Faraskour plant (site VF) (4.1%), in which Bacillariophyta represent 1.1, 3.2%, Chlorophyta represent 0.3, 0.7% and Cyanophyta represent 0.05, 0.2% at VB and VF respectively. The annual mean of total phytoplankton standing crop at out flow of El-Bostan plant (site VIF) (7050 cell/L) higher than that at out flow of Faraskour plant (site VIB) (770 cell/L). Consequently the conventional drinking water treatment plant is more efficient in phytoplankton removal than compact water treatment plant.
Key words: Phytoplankton, drinking water, drinking water treatment plant, removal efficiency, flocculation, sedimentation, filtration, disinfection
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