Wastewater treatment plant automation and real-time control have become important topics of research and development. Real-time control is nowadays considered a desirable goal for medium- to large-sized utilities for attaining better treatment efficiencies and improved compliance with discharge permit limitations. For an efficient implementation, real-time control must be supported by adequate modelling methodologies that take into full account the dynamic properties of the treatment system. This paper evaluates the requirements of such applications and the properties of available modelling approaches. Some applications examples are discussed.