Influence of Variation Dosage of Chemical Reagents in the Turbidity of Overflow from Sedimentation Process at Dewatering Plant of PT. Freeport Indonesia

Dewatering Plant at PT. Freeport Indonesia is located in Amamapare Island. The plant's objective is to reduce the moisture content of concentrate slurry by using vertical pressure air and disc filter -dryer circuit. Vertical pressure air and disc filter produce discharge water that called filtrate. Filtrate still contains high number of suspended solid so the filtrate is not possible to be discharge to the environment. Dewatering Plant of PT. Freeport Indonesia precipitates the suspended solid in the filtrate by using thickener-lamella-settling pond circuit until the suspended content less than 50 mg/L. Flocculant and coagulant are used to optimize precipitation process. Several test work performed to find the most optimum dose. The result shows that combination of flocculant-coagulant can decrease total suspended solid content in overflow from sedimentation process. The result also shows that increasing flocculant dose is not always followed by better result.