Influence of Heavy Metals and Non-Cohesive Sediments on the Flocculation Behavior of Kaolin

Flocculation of cohesive sediments are affected by various physical, chemical and biological factors. The present study investigated the effect of heavy metals on the flocculation of cohesive sediments and its resistance to breakage under the shear imparted by sand. Experimental investigations were conducted in a flocculator with varying speed agitator for various concentrations of Fe (II) (0mg/L, 0.1mg/L, 0.5mg/L, 1mg/L, 5mg/L, 10mg/L and 20mg/L) and sand (0%,10%,30%,40% and 50%) under different salinity conditions (0g/L, 15g/L and 30g/L). The floc characteristics were obtained using an image capturing and processing technique. The experimental results indicated that the addition of Fe (II) contributes to the floc formation as a result of aggregation of flocs, whereas the addition of sand to the Fe-kaolin suspension contributed to the breakup of flocs. The floc volume fraction of macroflocs were observed to increase with the increase in metal concentration. The increase in sand concentration led to an increase in the floc volume fraction of microflocs. Further the behavior of breakage coefficient of flocs on the addition of sand were analysed. It was observed that the breakage coefficient decreased with the increase in sand concentration. Further it was noticed that the flocs formed at higher Fe (II) concentration at high salinities possess higher breakage coefficient.