Application of stochastic modeling techniques to wastewater treatment processes real-time operation and control

The issue of real-time control of wastewater treatment facilities and sewerage systems has become a promising and active area of research in the last few years. However, in order to control and operate a wastewater treatment plant, a good representing model becomes necessary. Such a model should allow prediction of the future status of the system, and should also be able to adapt itself to the changing conditions in which the system operates. A wastewater treatment plant is a system whose behaviour is in part conditioned by its immediate past history: this is called a dynamic system. Dynamic systems modelling can be successfully achieved by means of stochastic processes, with a technology known as Time series analysis . This dissertation determines that is possible to develop a modeling of wastewater treatment operation based on stochastic relationships. In addition, this work investigates how these models can be usefully employed in the perspective of achieving real-time control of such facilities, and the practical implications the models can have on current design and engineering practices. In particular, this work shows that steady-state relationships between variables are not suitable, in general, to significatively represent time-variant processes. Models identified through time series analysis can be compared with traditional deterministic models expressed in differential equations. The identification of these models is relatively simple, and they can be easily updated to closely follow smooth variations in the behavior of the system. The resulting models are site-specific; that is, they are a functional consequence of the performance records of each treatment plant. This accounts for those unique conditions which are necessarily not considered in the general kinetic theory of the processes. This type of technique can be further implemented in control procedures that can be interactively used at a friendly level by skilled staff of treatment facilities, or even be completely automated, as already proven by applications in several areas of industry. This work outlines the requirements for such an implementation, and discusses the repercussions of the availability of real-time control technology on wastewater treatment facilities design