Flokulatsiooni

Flokulatsiooni, or flocculation, is a process in colloid and surface chemistry where fine particles suspended in a liquid collide and stick together to form larger aggregates called flocs. It typically follows a coagulation step and is used to enhance solid–liquid separation by sedimentation or filtration, improving clarity in water and wastewater treatment and in various industrial processes.

The process relies on several mechanisms. Coagulants such as aluminum or iron salts neutralize the electrical charges on particle surfaces, allowing them to come together. Flocculants are high molecular weight polymers that bridge closely spaced particles, forming a network of interconnected particles. Sweep flocculation uses the formation of a precipitated matrix to capture particles during rapid mixing. The combination of these mechanisms leads to the growth of flocs that settle more readily or are easier to filter.

Typical process steps include rapid mixing to disperse the coagulant, dosing of a flocculant, followed by slow mixing to promote floc growth. Flocculation efficiency depends on factors such as the type and dose of coagulant and flocculant, pH, temperature, mixing intensity and duration, and the characteristics of the suspended matter, including particle size and zeta potential.

Applications span municipal drinking-water treatment, wastewater treatment, and many industrial processes (pulp and paper, mining, food and beverage). Advantages of flokulatsiooni include improved turbidity reduction, reduced downstream filtration or sedimentation requirements, and shorter treatment times. Potential drawbacks include residual chemicals, polymer costs, and sludge handling considerations.