flokulering

Flokulering, or flocculation in English, is a chemical process used in water and wastewater treatment to remove suspended solids by promoting the aggregation of tiny particles into larger clumps called flocs, which settle more readily or can be removed by filtration. It is part of the broader coagulation–flocculation sequence that destabilizes colloids and enhances solid-liquid separation.

Process: After destabilizing colloids with coagulants such as aluminum or iron salts, gentle mixing (flocculation) promotes collisions and growth of aggregates. This step follows rapid mixing and precedes clarification by sedimentation or filtration. Flocculation is typically performed in tanks where shear is gradually reduced to allow flocs to grow without breaking apart. Jar tests or bench experiments are commonly used to optimize coagulant and flocculant dosages and mixing conditions.

Flocculants: Polymers such as polyacrylamide or other synthetic and natural polymers are used to bridge particles and strengthen floc formation. In drinking water treatment, inorganic coagulants (e.g., alum, ferric chloride) are often combined with organic polymers to improve floc strength and settling performance.

Applications: Flocculation is employed in municipal drinking water treatment, wastewater treatment, pulp and paper processing, mining and mineral processing, turbidity control, and sludge handling. It is also used in some food and pharmaceutical processes where clarification is required.

Operation factors: Key variables include pH, temperature, mixing intensity and duration, particle size distribution, and the concentrations of coagulants and flocculants. Optimization is frequently achieved through jar testing and monitoring of turbidity and settleability.

Outcomes: Effective flocculation yields larger, stronger flocs that settle faster and improve clarification and filtration efficiency, while improper conditions can produce small or fragile flocs that resist removal.