Response surface methodological approach to optimize the coagulation–flocculation process in drinking water treatment

Performing jar tests often requires carrying out a time consuming iteration procedure to find out the right amount of chemical for coagulation–flocculation process in water treatment plants. Applying the response surface method (RSM) in jar tests as an alternative to the conventional methods was investigated in this study. The purpose is finding out the optimum combination of coagulant dose and pH with respect to the highest removal efficiency of turbidity and dissolved organic carbon (DOC). The results achieved using poly-aluminum chloride (PACl) were compared to those achieved using conventional coagulant such as alum. The quadratic models developed for the two responses (turbidity removal and DOC removal) indicated that the optimum conditions to be PACl concentration of 0.11 mM at pH 7.4 and alum concentration of 0.15 mM at pH 6.6. Compromising to simultaneously optimize the two responses resulted in 91.4% turbidity removal and 31.2% DOC removal using PACl whereas 86.3% turbidity and 34.3% DOC were removed using alum. Confirmation of experimental results was found to be close to the prediction derived from the models. This demonstrates the benefits of the approach based on the RSM in achieving good predictions while minimizing the number of required experiments.

Research highlights▶ RSM is useful for optimizing the coagulation-flocculation process. ▶ PACl with high content of Al13 species promotes turbidity removal. ▶ Low coagulation pH promotes DOC removal. ▶ High coagulation pH promotes turbidity removal.