Optimal control of the activated sludge process

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Abstract
This paper assesses the potential benefits of optimal control applied to the activated sludge wastewater treatment process. The optimal control approach is motivated by the need to compromise between treatment efficiency and operational costs. In this sense this approach differs from a previous activated-sludge control scheme, in which only control effectiveness was taken into account. Two separate control problems are addressed, with differing scope and methodologies, but still in the optimality context. Dissolved oxygen control is considered first, and a discrete-time optimal output regulator is designed. Then the attention is focused on recycle sludge manipulation for which two different feedback schemes are evaluted. From the simulations it appears how the effectiveness of a control scheme depends almost entirely on a proper choice of the cost functional.