ABSTRACT
Lagoons substitute time for the many control variables available in an activated sludge system. As effluent requirements become more stringent, lagoons become less viable as primary treatment units and are better applied as contributing elements of more complex systems. A partial or completely mixed lagoon is one in which aerobic conditions are maintained throughout the basin. Reaction kinetics for ponds and lagoons are related to a once-through reactor configuration. An aerated lagoon can be used to treat industrial wastes containing dissolved organics and relatively low nondegradable solids content. Low reactor microorganism concentration dramatically affects lagoon performance, especially in winter conditions. Influent solids control is an important consideration in aerated lagoon design. The effluent from aerobic lagoons is high in biological oxygen demand5 and suspended solids. Facultative lagoons consist of an upper aerobic layer, a lower anaerobic layer, and a middle or transitional layer buffering the two environments.
