Identification and control of nutrient removing processes in wastewater treatment plants

Today the use of online control for wastewater treatment plants is very low. A main reason is the lack of quality of the data, and the fact that more sophisticated control strategies must be based on a model of the dynamics of the biological processes. This paper discusses the historical reasons for the limited use of modern control strategies for wastewater treatment plants. Today however, online nutrient sensors are more reliable. In the present context the use of online monitored values of ammonia, nitrate and phosphate from a full scale plant are used as the background for discussing the possibility of using statistical methods for identifying dynamical models for the biological processes. These models can then be used for simulating various control strategies and the parameters of the controllers can be found by off-line optimization. Simulation studies have shown that considerable savings are possible by using modified online control strategies