Primary Treatment is the first process that takes place, it's usually the operation preformed to remove those materials that separate easily.The web definition of Primary Treatment is: The first stage of waste water treatment, consisting of the removal of a substantial amount of suspended matter by using, Sedimentation, Flocculation, Screening or similar methods.
Sedimentation takes place in a settling tank or a clarifier. It allows many suspended particles to settle out of water or waste water while slowing going through the tank and providing a source of purification.A large about of sludge is usually found at the bottom of the tank and is periodically removed.
Flocculation is the action of binding large particles into clumps. It's where Colloids form into flakes or floc, colloids are usually dissolved into a liquid, they do this by genitally mixing the coagulated water this is also called the hydrodynamic process. Flocs or flakes are supposed to grow to either 0.1 or 2.0mm so that it can be removed by sedimentation.
Screening, removes relatively large solids in a primary treatment facility. It is most commonly used by food processing plants and reduces the amount of solids being discharged. During the Screening Treatment, wood, dead animals, and rocks get in the way and have to be removed to keep the process going.