Optimal Real-time Activated Sludge Regulation

Abstract

An application of optimal control techniques in regulating a conventional activated sludge process (Figure 1) is presented. In this process, organics in the influent wastewater (substrate) serve as energy source for the aerobic growth of microorganisms (biomass or activated sludge) in the biological reactor. The resulting mixed liquor is purified (clarification) by settling of the microbial floes in a following tank (settler). The thickened sludge is recycled to the biological reactor to sustain the biomass amount. To maintain a constant amount of biomass in the system, excess biomass is regularly removed (wastage). The process can be regulated by varying certain inputs such as the wastewater feed point, sludge recycle and wastage rates, aeration rate, and on-line sludge storage and resupply rates. The scope of this paper is to present an application of an optimal control method to a detailed activated sludge model, consisting of a multicomponent biological reactor and a dynamic multilayer settler. A real-world implementation for the Yellow River/ Sweetwater Creek wastewater treatment plant in Gwinnett county is presently being conducted.