Flokulation

Flokulation, commonly spelled flocculation, is the process by which colloidal or fine suspended particles aggregate into larger, easily removable clumps called flocs. The term is used across environmental science, chemistry, and engineering and often appears as an alternative spelling in some languages. In practice, flokulation is the second stage in many water- and wastewater-treatment sequences, following coagulation.

The mechanism involves destabilizing the surface charge of particles and then promoting particle–particle attraction. Coagulation uses chemical coagulants to neutralize charges, reducing repulsion among particles. Flokulation follows with gentle mixing that enables bridging and aggregation, forming larger flocs that settle by gravity, float by buoyancy, or be captured by filtration. Flocculants such as polyacrylamides or natural polymers can assist by linking particles together, a process known as bridging.

Several factors influence flokulation. Particle size, surface charge, and the pH and ionic strength of the water affect stability and aggregation rate. Mixing intensity and duration must be balanced: insufficient mixing yields weak flocs; excessive stirring can break them apart. The choice and dose of coagulants and flocculants, the presence of natural organic matter, temperature, and flow conditions also play important roles.

Applications include drinking water treatment, wastewater treatment, sludge dewatering, and various industrial processes where solid–liquid separation is required. Flokulation is typically evaluated using jar tests, turbidity and color reduction measurements, and analyses of floc size distribution and settling characteristics.