MUNICIPAL WASTEWATER TREATMENT IN THE NETHERLANDS PRAGMATICALLY CONTROLLED

Almost every treatment plant in The Netherlands with high nutrient removal has some kind of control strategy by using one or more sensors. The use of instrumentation and control (I&C) in The Netherlands can be characterised by a pragmatic approach. Due to the fact that wastewater treatment plants are designed in a conservative way, many WWTP's have some overcapacity. In this situation control methods are kept simple because too often it was concluded that advanced I&C approaches could not improve the performance of the system concerning effluent quality and energy consumption when compared with a simple control method with for example only a DO sensor. Instrumentation and control is mainly used to guarantee that the WWTP is functioning according to the design. Different sensors are often already installed for monitoring the different processes. By implementing these sensors in a more advanced control strategy, still some important benefits can be gained by influencing positively the stability of the system. A proper definition of control goals is with that an important first step in the design of control units. This paper gives an analysis concerning the situation with I&C in The Netherlands for municipal wastewater treatment and it provides the reader with some suggestions for a more successful introduction of instrumentation and control. The development of a control unit for the sludge dewatering process serves for this as a proper example.