Wastewater treatment plants are systems, in which physical, chemical and biological processes run in combination. Increasing demands in terms of efficiency with, at the same time, increasing pressure on costs require continuous process optimisation.
The reasons for this lie, above all, in the complexity and the high degree of non-linearity of the biochemical processes. These follow exponential growth laws, with the result that the composition and the activity of the activated sludge are subject to seasonal fluctuations and even fluctuations that are dependent on the time of day. For these reasons, a plant may react very differently to the same control command at different times.
If, in addition, the need for multiparameter control is taken into account, then those methods that are widespread in traditional automation technology (e.g. PI controllers) cannot ensure optimum operation.
The basic principle of state control is based on the steps described below. Various computional intelligence (CI) and/or statistical processes are thereby combined in order to jointly exploit their benefits.
Classification of the Operational Situation:
>„Classification of the Operational Situation “
The measured values for the plant are analysed and summarised in classes. This can be prescribed by a control system or determined automatically by cluster methods such as k-mean clustering. Thus the class, in each case, describes a specific operational situation in relation to the plant.
State Transfer:
Following classification of the operational situation the latter must be translated into a state for the plant. In addition to the current operational situation, the state for the plant also takes into account all previous states. As a result, operational situations over a fairly lengthy period of time can also be evaluated. In addition, the state transfer allows synchronisation with other parts of the system. The state transfer is translated using state-recording machines.
Selection of the Control Strategy:
Following determination of the state of the plant it is possible to select suitable control strategies for the given state. This can, for example, be carried out by selecting desired values for the subdivided control system.
