The material presented here is intended to provide an introductory textbook in control and instrumentation technology for waste water treatment (WWT) plants. It is aimed at WWT plant operators, process design and control engineers, works managers and those who are involved in the design, installation, commissioning and operation of WWT plants. It is also a reference source for students. Subject covered include control theory, WWT plant modelling and simulation, supervisory control, data management, sensors, virtual instrumentation, expert systems, neural network and fuzzy logic.