Explain Rapid Mixing Tank

• For the chemical reactions to occur, the chemicals must be mixed with water
• for both coagulation and softening we need mixing of chemical with water
• Mixing or rapid mixing is the process in which chemicals are quickly and uniformly dispersed in water (instantaneously)
• for coagulation and softening processes precipitates form during the mixing
• the precipitates formed must be brought into contact with one another and colloids so that they can agglomerate and form larger particles called flocs - this process is called flocculation and is accomplished by slow, gentle mixing (rapid mixing may break up the flocs)
• Degree of mixing is measured by velocity gradient G (amount of shear taking place). Higher the G, the more violent the mixing

Design Criteria  

Rapid Mix 

Volume   = Flow rate (Q)*detention time 

Detention is in the order of seconds 30-120 seconds

Mixing basin is typically a cube