The Effect of Coagulant Dosage on Characteristic Values of Filtration : Aluminum Sulfate and Hara-Gairome Clay-Water Slurry

Filtration processes of Hara-Gairome clay-water slurry were studied by dosing aluminum sulfate as a coagulant, to examine the effect of coagulant dosage on characteristics of filtration. With increasing the dosage of coagulant, the average specific resistance of cake decreased and the optimum dosage was obserbed as in the other coagulation operations. At the optimum condition, average specific resistance decreased until one-third or seventh of its original slurry. In accord with the effect of coagulant dosages and pH values on ζ-potential and capillary suction time, it was confirmed that principal mechanism in the coagulation was neutralization of surface electric charge on the particles. Even for such the coagulated slurry, the compression permeability tests gave rational experimental results. Theoretically predicted values of filtration characteristics based on the compression-permeability data, indicated favorable coincidence with the experimentally measured values of them. A new conventional method was proposed to predict the filtration process of coagulated slurry based on the process of original, non-dosed, slurry and CST measurement. In spite of rough estimation, the method might be useful to predict the degree of improving filtration process. The calculated process and its experimental values of dosed slurry were compared.