Coagulation process optimization for turbidity removal improvement at the Teluk Buyung WTP using Response Surface Methodology with Box-Behnken Design

. The effective operation of the coagulation process in the water treatment plant (WTP) is essential in determining the overall performance of the subsequent process. The coagulant dose is critical in affecting coagulation performance. Due to the fluctuations in raw water quality and the infrequent use of jar tests, Teluk Buyung WTP improperly implemented the coagulant dose, which prompted this investigation. This study aimed to identify the optimum coagulant type and develop an optimization model based on the selected coagulant. The optimum coagulant type was determined in the pre-liminary study, with Polyaluminium chloride (PAC) selected as the coagulant that achieved turbidity removal up to 99.81% at a dose of 40 mg/L and a cost-effective production cost of 4.6 x 10-5 USD/liter. The optimization process was conducted by developing a coagulation process model using PAC as the selected coagulant, with critical factors affecting the process including pH, turbidity concentration, and coagulant dose. The coagulation process optimization was performed by using response surface methodology (RSM) with a Box-Behnken design (BBD). The optimal conditions of PAC in the desirability test resulted in turbidity removal of 99.94% with a PAC dose of 150 mg/L, pH of 7.14, and a residual of 0.04%. The optimization of the coagulation process yielded a quadratic model with R2 of 0.996, an R2 prediction of 0.983, and a significant lack of fit test (p = 0.28). The findings of this study can be further implemented to improve turbidity removal in the coagulation process at the Teluk Buyung WTP.