What is the mechanism of action of flocculants?

Colloidal particles in water are minute, and their surface hydration and charge impart stability. When flocculants are added to water, they hydrolyze into charged colloids that form double-layer structures with surrounding ions. Rapid agitation after chaical addition increases the frequency and opportunities for collisions between colloidal impurities and the hydrolyzed flocculant aggregates. Under the action of flocculants, impurity particles in water first lose stability, then coalesce into larger aggregates, which subsequently settle or float in separation facilities.

The product GT of the velocity gradient G generated by agitation and the agitation time T indirectly represents the total number of particle collisions throughout the reaction period. Adjusting the GT value controls the coagulation reaction efficiency. Typically, GT is controlled between 10⁴ and 10⁵. Considering the influence of impurity particle concentration on collisions, the GTC value can serve as a control parameter characterizing coagulation efficiency, where C represents the mass concentration of impurity particles in wastewater. A GTC value around 100 is recommended.

The process of rapidly dispersing flocculants throughout the water and uniformly mixing tha with the entire wastewater stream is termed mixing. The interaction between impurity particles in water and flocculants, leading to the loss or reduction of stability through mechanisms such as double layer compression and electrostatic neutralization, and the subsequent formation of microflocs is called coagulation. The process where these microflocs grow into larger flocs through bridging adsorption and sediment entrapment, aided by bridging substances and agitation from water flow, is called flocculation. Mixing, coagulation, and flocculation collectively form the coagulation process. Mixing typically occurs in mixing tanks, while coagulation and flocculation take place in reaction tanks Zaozhuang Kairui Water Treatment Co.,Ltd..