Steam power plants consist of systems such as Water Treatment Plant (WTP), boiler, turbine-generator, and balance of plant. WTP system consists of sedimentation, desalination, and demineralization. The coagulation mechanism triggered by the mass grave of suspended solids during the sedimentation process, and if it is less than optimal, so will be modified by injecting coagulant-flocculant chemicals. The most common problem is the high dose chemicals used in the rain and tidal sea conditions. However, the output water quality that produced still does not reach the standard requirements. This condition would affect the high costs of water treatment operations. It also would have an impact on the poor feed the next system. The jar-testing technique is research using process and operational variables that theoretically influence the efficiency of the coagulant-flocculant such as doses, setting times, and rotates agitator. Evaluation of experiments using water quality criteria and data results processed by AHP and AHP-TOPSIS. The sensitivities of both methods are analyzed thus compared to select a consistent alternative that obtained sequence the first alternative for D60W30P80 and the second alternative for D40W20P80. The optimal sedimentation process could potentially save 40-60% of the water treatment operational cost while operating conditions achieved.