In order to inactivate Pseudomonas aeruginosa in raw waters, we investigate the efficiency of primary chlorination alone and combined chlorination and clarification in surface water naturally containing P. aeruginosa. Final disinfection was performed in clarified surface water and groundwater both contaminated with P. aeruginosa. The results obtained under laboratory conditions show that coagulant aluminum sulfate (AS) and cationic polymer polyelectrolyte contribute significantly to reducing turbidity with the inactivation of cultivable cells of P. aeruginosa in different water samples. Our findings also suggest that while chlorination may be a satisfactory method for controlling and preventing P. aeruginosa growth in water intended for human consumption, it does not eradicate all cultivable bacteria in raw surface water. P. aeruginosa was nonetheless shown to be relatively sensitive to sodium hypochlorite, and the effectiveness of chlorine was greater in natural groundwater than in clarified surface water.