The behaviour of floc in the flocculation of kaolinite clay

Abstract

Several experimental runs were performed to investigate the effect of kaolinite particle size, flocculation time, velocity gradient, coagulants dose and initial turbidity on the solid removal and floc size or floc formation of suspended solid. The coagulants used were alum, polyelectrolyte (cationic) or a combination of both. Different classifications of clay particles are used in the present work of grade less than 10, 20 and 40 μm. The particle size of 10 μ at 200 NTU initial water turbidity was used to study the effect of flocculation time, (1-20 min) on floc formation size and flocs number at optimum velocity gradient. The size distribution of flocs was studied as a function of kaolinite concentration in the range 1-3 mg/1 at 20 min flocculation time in case of alum and polyelectrolyte. The results are presented graphically by three-dimensional and contour plots showing the floc number as a function of coagulant dose and flocculation time. The results are also plotted to show the required turbidity as a function of velocity gradient and flocculation time at optimum coagulant dose to locate the overall optimum working conditions. It is found from various experimental results that floc size or floc formation and growth are the principal criteria that effect the flocculation process.