Algorithm for Optimal Activated Sludge Operation

A method for determining the minimum cost operation of an activated sludge wastewater treatment plant is developed and applied to a plant in Erie County, New York. The plant includes an aerated grit chamber, two aeration basins, two secondary clarifiers, two solids contact clarifiers, a flotation thickener, sand-drying beds, centrifuge, an aerobic digester, two gravity sand filters, and chlorination-reaeration facilities. The complex method of constrained optimization is modified for discrete-valued variables and used with nonlinear cost and process equations to determine the minimum cost operation of the plant for a specified 12-month flow sequence. The results from the optimization are compared with actual operation of the plant.