No phytoplankton should be present in treated drinking water because of their production for bad smell and toxins that may pose hazards to animals and human upon consuming this water. This study describes the efficiency of alum and lime-alum treatments for removing phytoplankton from the Nile river water used as a source of drinking water in Egypt. The results showed that alum could not precipitate all phosphate nor coagulate waterblooms-forming cyanobacteria present in the water sample. Conversely, lime-alum treatment precipitated much more phosphate than alum did, and coagulated all phytoplankton present in the water samples including those could not be coagulated by alum. Furthermore, lime-alum treatment did not change the pH of the water during all the experiment period. Hence, it is advisable that lime-alum be used instead of alum during water treatment process in Egypt.