This investigation investigates the optimization of coagulation processes in water treatment using experimental designs that integrate controlled and obstructing factors. The research is dedicated to enhancing the efficacy of turbidity elimination by conducting container experiments that replicate conditions pertinent to the Thailand Metropolitan Waterworks Authority. The concentrations of coagulants, PolyAluminum Chloride (PACl) and alum, and the rotational speed of the turbine are among the primary factors examined. Nephelometry Turbidity Units (NTU) are used to quantify the response variable, water turbidity. The obstructing factor of untreated water with variable initial turbidity levels mitigates the variability in water quality. The variability in water quality is mitigated by the obstructing factor of untreated water with variable initial turbidity levels. In order to guarantee the resilient performance of the process, a desirability function is implemented to regulate the mean and standard deviation of water turbidity levels. A factorial design is employed to systematically evaluate factor interactions in order to identify the optimal coagulation conditions. The results indicate that turbidity reduction is considerably improved by specific combinations of turbine rotational speed, PACl, and alum concentrations, resulting in more efficient water treatment. The new operating scenario exhibits superior performance in terms of both central tendency and dispersion effects. The initial water turbidity blocking factor significantly influences the efficacy of the coagulation process, underscoring the significance of integrating input variability into treatment optimization. This study offers practical suggestions for enhancing coagulation processes and valuable insights into the application of advanced experimental designs in water treatment, thereby promoting the sustainable and reliable management of water supplies.