32. Activated Sludge Mixed Liquor Air Secondary clarifier w/w Waste Activated Sludge (WAS) Return Activated Sludge (RAS) Treated w/w Discharge to River or Land Application
t d = approximately 6 - 8 hr Long rectangular aeration basins Air is injected near bottom of aeration tanks through system of diffusers Controlled by wasting a portion of microorganisms
Facultative zone: aerobic during day (photosynthesis occurs) anaerobic at night (respiration) Rely on wind action for reaeration wastewater enters from bottom