M. Fikar, Dynamic Optimisation of Small-size Wastewater Treatment Plants, MF0101, Laboratoire des Sciences du Genie Chimique, CNRS, Nancy, France, Final report of the program: Accueil de chercheur etranger de haut niveau, Ministere de la recherche, 2001.

In this report we make a summary of the research activities in the framework of the program ``Accueil de chercheur \'etranger de haut niveau'' of the ``Minist\`ere de la recherche''. The research subject was dynamic optimisation of small-size wastewater treatment plants. This subject has been chosen for its importance arising from both regulation fulfillment and cost aspects of the plant operation.

The aim of the work is to determine an optimal duration of the aeration and non-aeration sequence which will minimise the operational costs as well as satisfy the constraints specified by the EU directives.

In the second chapter, a typical model of a small-size wastewater treatment plant is described. The model consists of a single aeration basin where oxygen is supplied by surface turbines. The initial model has been described as a hybrid discrete/continuous system. Such systems are traditionally more difficult to optimise and control and therefore one of the aims was to reformulate the model so that it is described as a continuous system only.

In the third chapter, the dynamic optimisation problem is formulated. Basically, as the aim is to reduce the energy consumption, mathematical definition of this aim is presented and possible difficulties in the solution are discussed.

Chapter 4 describes in more detail the implementation issues of the optimisation, transformation of the original dynamic optimisation to a static optimisation as well as an approach of gradient calculations needed in the nonlinear programming problem.

Chapter 5 presents simulation results obtained and Chapter 6 draws conclusions and gives future perspectives.

A user manual to the dynamic optimisation package \texttt{DYNO} is given in the Appendix, together with some examples.