Jar test experiment

The two basic terms which can exactly explain the happenings of this experiment are “Coagulation” and “Flocculation“.
1. Coagulation: It is the process of addition of a chemical to de-stabilize a stabilized charged particle.
2. Flocculation: It is a slow mixing technique which promotes agglomeration and helps the particles to settle down. So the “slow mixing” step is needed in the present experiment.
Generally we encounter very fine and charged clay like particles in water treatment which should be removed before we continue for further processes. These impurities do not settle by gravity when the water is passed through a sedimentation tank. The reason being that these are charged particles, they repel each other and just stay.
When Coagulant like alum solution is added to water, the molecules dissociate to yield positive and negative charges like SO42- and Al3+ in alum. These charged species combine with the charged colloidal particles to neutralize the charge of the component producing turbidity, and then these components are conglomerated and settled out