Activated Sludge

A type of treatment where the wastewater and sludge containing microorganisms are mixed together and have air bubbled through them in a treatment tank known as a reactor. The microorganisms use the organic matter in the wastewater as food, breaking it down into smaller molecules. The introduction of air speeds up the process. The sludge that accumulates in the reactor contains billions of actively growing bacteria. It is the bacteria that make the sludge turbid and brown. This sludge is routed to a settling tank (also called a clarifier), where the bacteria are separated from the treated water. A portion of this “activated sludge” is returned to the beginning of the reactor to continue the process as influent wastewater enters the reactor.