Operating Parameters Affecting the Formation of Kaolin Aerated Flocs in Water and Wastewater Treatment

The formation of aerated flocs (aeroflocs) and the main operating parameters involved were studied to improve the rapid solid/liquid separation by flocculation-flotation. A continuous flow system at the laboratory scale was used that coupled micro-bubbles dissolved air flotation and a flocs generator reactor (FGR). The aerated floc characterization technique was employed to characterize the aggregates obtained using a non-ionic polymer (920SH SNF-Floerger (R)). Flocculation-flotation studies evaluated the effect of the suspension flow rates (Q(s): 0.12, 0.24, 0.36, and 0.48m(3)/h, the air/solid rates (A/S: 0.01, 0.02, 0.03, and 0.04 mg/mg) and the forms of flocculation (flocculation form I: a primary flocculation after coagulation inside a stirred tank, followed by mixture with air bubbles into the FGR and flocculation form II: full flocculation in the FGR). The main results demonstrated that the mixture of particles, air micro-bubbles and polymeric macromolecules in a proper turbulent flow inside the FGR was the key to the effective generation of very light aerated flocs. These aggregates had higher uprising rates, which ranged between 70 and 150 m/h and represented 83% of the flocs population at an air/solid rate of 0.02 mg/mg and a flow rate of 0.24m(3)/h. It is believed that, by maximizing operating parameters, improvements are achieved, mainly, both increasing the removal efficiencies and the design of the equipment that can be more compact requiring fewer areas than conventional units.