ABSTRACT
I N wastewater treatment, activated-sludge processes are used for both secondary treatment and complete aerobic treatment without primary sedimentation. Activated sludge refers to biological treatment systems that use a suspended growth of organisms to remove BOD5 and suspended solids. The process requires aeration equipment, aeration and settling tanks, and return and waste activated sludge support equipment, such as pumps and flow measurement. Wastewater is fed continuously into an aerated tank, where the microorganisms metabolize and biologically flocculate the organics (see Figure 1 1.1). Microorganisms (activated sludge) are settled from the aerated mixed liquor under quiescent conditions in the final clarifier and are returned to the aeration tank. Clear supematant fiom the final settling tank is the plant effluent.
