Abstract: Coagulation-flocculation step is one of the most important steps during surface w ate r tre atm e n t. Che m ic al co ag ul an ts are o rdin ary use d such as al um . Howe ve r, the se chemical coagulants are dangerous to environment and human health. Natural coagulants derived from natural sources receive much attention during last years. This study aimed to isolate new bacterial exopolysaccharides from Bacillus licheniformis, B. insolitus and B. alvei to be used as natural coagulants during coagulation-flocculation process. Efficiency of extracted bacterial exopolysaccharides was examined through removal ability of bacterial indicators and some physicochemical parameters of River Nile water samples. Bacterial exopolysaccharides showed great removal percent when used as sole coagulant materials. Addition of alum to bacterial exopolysaccharides enhance removal efficiency
