flokkulering

Flokkulering, commonly translated as flocculation, is a treatment process in which colloidal or finely divided solids in suspension aggregate into larger, settleable flocs. The process follows coagulation and relies on neutralizing particle surface charges and enabling interparticle bonding, so that small particles combine into larger aggregates that can be removed by sedimentation or filtration.

Mechanisms include charge neutralization, where multivalent cations from coagulants reduce electrostatic repulsion, and bridging, where long-chain polymers bind multiple particles. The choice of agents and conditions such as pH and ionic strength determine the dominant mechanism and floc strength. Flocs are formed under gentle shear; excessive stirring breaks them apart.

Process and equipment: Flokkulering typically occurs in three stages: rapid mixing to disperse coagulants; slow mixing or paddle mixing to promote floc growth; and subsequent settling or flotation for solid–liquid separation. Equipment includes rapid-mix tanks, flocculation basins, and clarifiers or flotation units; lamella settlers increase settling capacity.

Chemical agents: Coagulants (e.g., aluminum sulfate, ferric chloride) destabilize particles; flocculants (e.g., cationic polyacrylamide) promote bridging. Both inorganic and organic additives are used, sometimes in combination. Optimization involves dosage, contact time, temperature, and mixing intensity.

Applications: Flokkulering is used in drinking-water treatment, municipal and industrial wastewater treatment, mining effluents, and pulp and paper processing. Performance is assessed by turbidity, particle size distribution, zeta potential, and residual coagulant or polymer.