The colloidal particles in sewage are small, and the surface is hydrated and charged, making it stable. After adding cationic polyacrylamide into water, it hydrolyzes into charged colloid and surrounding ions, forming micelles with double electric layer structure. The chances and times of collisions between colloidal impurity particles in water and the micelles of cationic polyacrylamide hydrolysis were promoted by rapid stirring after dosing.
Under the action of cationic polyacrylamide, the impurity particles in the water first lose stability, and then condense into larger particles, and then precipitate or float in the separation facility. The product GT of stirring velocity gradient G and stirring time T can indirectly represent the total number of particle collisions during the whole reaction time, and the coagulation reaction effect can be controlled by changing GT value. Generally, GT value is controlled between 104-105. Considering the influence of impurity particle concentration on collision, GTC value can be used as the control parameter to characterize coagulation effect, where C represents the mass concentration of impurity particles in sewage, and it is recommended that GTC value be about 100. Mixing is a process that promotes rapid diffusion of cationic polyacrylamide into the water and uniform mixing with all wastewater.
The impurity particles in water react with the cationic polyacrylamide and lose or reduce its stability through the mechanism of double layer compression and electroneutralization. The process of producing a microflocculent is called coagulation. Under the agitation of bridging material and water flow, the process of flocculation is called flocculation.
