Simplified Optimization of Activated Sludge Process

The objective function minimized is the total annual cost associated with the primary settler, aeration basin, blowers, final settler, and recycle pumps. The key to the application of DP is the proper selection of state and decision variables. The input state to the primary settler is the waste strength, and the decision variable is the removal efficiency, giving the strength of the primary effluent as the input state to the aeration basin. Both the decision variable and the output state for the aeration basin are the mixed liquor suspended solids (MLSS) concentration thus fixing the required volume. Utilizing the MLSS concentration as the input state to the final settler allows the use of the recycle ratio as the decision variable, thereby fixing the required surface area. A tabular format is presented whereby the optimization may be performed simply and efficiently without the use of a computer.