A study of water clarification process in industrial water treatment system using a polymerized inorganic coagulant (aluminum hydroxychloride) is made in this paper. Initially, the most important conceptual elements of the stages of clarification process (coagulation, flocculation and sedimentation) are established. Then, it identifies the major conventional coagulants used in water treatment and the polyaluminum chlorides (PAC's) are mentioned as part of a new generation of alternative coagulants whose use has increased in recent decades because of their better performance with respect to conventional coagulants; technical and operational aspects to be considered when implementing a water clarification process using a PAC as coagulant are specified. Finally, some comparative data of water clarification process real operating conditions, from a previous work, which replaced a conventional coagulant (aluminum sulfate) by aluminum hydroxychloride are presented and a better performance of the process after the replacement is proved.