Optimal Allocation of Artificial Instream Aeration

In order to satisfy a given DO standard during short steady-state periods of low flow and high temperature, a system of mechanical aerators has been shown to be more effective than advanced wastewater treatment. Different water quality models are available at present, among which the so-called plug-flow models are of particular interest because they are the simplest ones. For an extremely large class of this type of models some structural properties of the optimal solution of the problem are proved. By means of these properties an algorithm for the solution of the allocation problem is first derived. Then, it is shown how the problem can be decomposed into a set of independent and easier subproblems when the aeration cost does not exhibit economies of scale. Finally a realistic application to the Rhine River is described.