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Effect of Slurry Aeration on Coagulation: An Application of Irregular Factorial Design Analysis

The effect of the aeration on the coagulation of a bentonite suspension was tested in this study. The experimental runs for this coagulation work was formed with the help of the irregular factorial design. Based on this irregular fractional design, a statistical model (R 2 = 92.65%; p-value<0.05) was computed to interpret the main effects and interactions of the independent parameters: pH, aeration, and Al-coagulant. The suspension pH was determined as the most effective parameter in this system since the degree of the hydrolyses of aluminium directly varies as a function of pH. Therefore, the increase in the suspension pH resulted in the higher sediment volumes whereas the minimum sediment volume was obtained at pH 5. Furthermore, the interaction effect of the product: pHxaeration in the statistical model was very critical for the performance of the process. Especially, at acidic pH levels, the aeration adversely affected the sediment formation after the coagulation. 3-D response surfaces of the estimated model also showed that the maximum amount of the Al-coagulant should be added at pH 5 and no aeration should be applied for the minimization of the sediment volume.