Algal population of NileRiver water is mainly composed of diatoms, green and blue-green algae (cyanobacteria). Percentage composition of algal species was in order diatoms > green algae > cyanobacteria. The conventional water treatment operations lead to the average removal of algae in the ratio of 92 %, 87%, and 77% for diatoms, green and cyanobacteria, respectively. Algal composition of the treated water was subjected to a wide variation after sedimentation and sand filtration. A relative increase in the percentage composition of green algae and cyanobacteria was recorded. Change in algal composition after water treatment operations reflects the wide variation in algal structure and their community.